“An Essay on Criticism” written by Alexander Pope is a/an -

An Essay on Criticism, didactic poem in heroic couplets by Alexander Pope, first published anonymously in 1711 when the author was 22 years old.

Alexander Pope, (born May 21, 1688, London, England—died May 30, 1744, Twickenham, near London), poet and satirist of the English Augustan period.
He is best known for his mock heroic poetry.
Some of his famous works are:
- The Rape of the Lock (1712–14),
- The Dunciad (1728), and
- An Essay on Man (1733–34).
He is one of the most epigrammatic of all English authors.

Source: Britannica.com